It's more than changing endings, it's changing the genus in the
first place that I object to. It's all very well naming things, but
to change the names subsequently seems unjustified.

That depends on whether it's arbitrary or uninformative. I know cases
of bees described in the genus Vespa, and wasps described in the
genus Apis - surely, it's highly worthwhile to have the present-day
name reflect more accurate placements! Conversely, we presently have
occasional trash taxonomists who arbitrarily place every species into
its own genus solely to boost their own egos - not merely
unjustified, but egregiously unscientific. Change in the former case
is good, while the latter is bad. You can't generalize. However, this
much CAN be said: if your objection is to the latter scenario, where
self-publishing hacks are flooding the literature with new generic
names that are garbage, then there are countermeasures the taxonomic
community can take BESIDES fixing names as invariant.